Embodiments of the present invention relate in general to measuring concentrations of dispersed phases in a flowing mixture. More specifically, but not by way of limitation, embodiments of the present invention provide for selectively wetting and/or coalescing the dispersed phase onto a sensor, measuring deposition and/or a rate of increase of an amount of the dispersed phase collected on the sensor and using the amount of deposition and/or the rate of collection of the dispersed phase on the sensor to determine or monitor a concentration of the dispersed phase in the flowing mixture.
It is often very important to know/monitor a concentration of constituents/contaminant or the like dispersed in a fluid mixture. For example, environmental regulations may require monitoring of liquid contaminants dispersed in a fluid, such as water or the like. Environmental regulations and laws may require certification from a party seeking to pump a fluid into the environment, such as disposal into a body of water, an underground formation, an underground reservoir and/or the like, regarding the purity and/or amount of contamination of liquids being introduced/re-introduced into the environment. As such, reservoirs, inputs to reservoirs, fluids to be dispersed into the environment and/or the like may need to be monitored/tested to determine the amount of dispersed contaminants within the reservoirs or being dispersed into an environment. For such monitoring/testing/certification purposes, because of the sensitivity of an environment, regulations may often require monitoring/measurement of very small concentrations of dispersed phases in a liquid, where such concentration may be of the order of several to 100s of parts per million.
In the hydrocarbon industry, there are several oilfield applications where it may be useful or legally required to know the concentration of a dispersed phase in a fluid, which fluid may be a flowing fluid. For example, when disposing of water produced from and/or used in a wellbore for producing hydrocarbons, the disposal location may be the sea, a disposal aquifer or an injection zone in the reservoir. Such disposal into the environment may require the water to contain a dispersed phase contamination, which in the case of water associated with an oil well may comprise oil droplets, below a certain threshold. Furthermore, subsurface disposal of such water may require the dispersed phase contamination, often referred to as the oil-in-water concentration, to be below a determined/specified concentration so as to minimize potential injectivity loss due to fouling of the injection zone by the oil. In other aspects of the hydrocarbon industry, initial detection of water being produced from a hydrocarbon wellbore may be important in oil and gas/condensate wells for process and pipeline control. This may be especially true in the latter type of well where hydrate inhibitors such as methanol are added. In such wellbores, poor or non-existent measurements of water content in produced fluid mixtures may lead to very conservative and costly procedures being unnecessarily used.
Existing online liquid contaminant monitoring devices suffer from limitations. These limitations may include the cost of the apparatus, the sensitivity of the sensing apparatus to adverse/hostile conditions, the use of an indirect physical process that requires a fluid calibration to determine a contamination value to arrive at the dispersed phase concentration—such as an oil-in-water concentration, a water-in-oil-concentration and/or the like—the inability to provide an instant measurement of the dispersed phase concentration, poor low concentration sensitivity and/or the like.
Off line measurements of dilute dispersions involve sampling a portion of a fluid followed by contaminant isolation using titration, solvent extraction and/or the like and subsequent measurement of the isolated contaminant. Such offline processes may be costly, cumbersome, time consuming, do not provide for real-time monitoring of a fluid mixture and/or, in the case of the hydrocarbon industry, may not provide for monitoring at the wellsite or at a remote pipeline/reservoir location.